Method of recording in a disk memory and disk memory system

Abstract

A method of recording numerical information in a plurality of disk units, in which the bits of each word of numerical information are transmitted simultaneously, each bit being allocated to a unit associated with the weight of that bit in that word, and a memory system for implementing the method, including a main controller (2) provided with a selector enabling the distribution and synchronization of the information signals.

What is claimed is: 
     
       1. A method of storing information in and retrieving information from a memory system which includes a plurality of disk units and a controller for the disk units, the information being in the form of a sequence of words, each word comprising a plurality of information bits, the method comprising calculating from the information bits of each word associated transversal error detection and correction bits; allocating each information bit of the word and each associated transversal error detection and correction bit to separate disk units of said plurality of disk units; simultaneously transferring the bits in parallel to the allocated disk units; storing each bit in its allocated disk unit at a logical address corresponding to the word; and, upon retrieving the word, using the associated error detection and correction bits for detecting and correcting transversal errors in the word. 
     
     
       2. The method of claim 1 further comprising detecting a defective disk unit and, in response to a defective disk unit being detected, automatically reconfiguring the system by allocating a reserve disk unit to replace the defective disk unit; retrieving the bits stored in the defective disk unit; correcting transversal errors in the retrieved bits; and transcribing the retrieved bits after correction into the reserve disk unit. 
     
     
       3. The method of claim 2, wherein a sequence of words forms a block of information, and the method further comprises assigning a block address to a block of information; transferring to each disk unit a sequence of bits corresponding to said sequence of words; temporarily storing the sequence of bits in a direct access memory in each disk unit, each bit being stored at a memory address which is a univocal function of the block address and of the position of such bit in the sequence of bits; transferring the bits in series from the direct access memory to a track of a disk within the disk unit to store the bits on the track, the track having an address which is a function of the block address, a function of the memory address of a first bit transmitted to the track, and a function of the number of a first sector of the track; and wherein a word of information associated with a logical address is read, beginning at the memory address of the direct access memory after transcription into the direct access memory of the entire block of information. 
     
     
       4. The method of claim 3, further comprising producing a longitudinal error detection and correction bit for each sequence of bits; and storing said longitudinal error detection and correction bits along with the information bits which form said sequence of bits. 
     
     
       5. The method of claim 4, wherein said detecting of a defective disk unit comprises detecting transversal and longitudinal errors in a sequence of bits retrieved from the defective disk unit; and comparing the errors to a predetermined criterion. 
     
     
       6. A memory system for storing and retrieving information in the form of a sequence of words, each word comprising a plurality of information bits, the system comprising a plurality of disk units; a controller for controlling the disk units; means for calculating from the information bits of each word corresponding first transversal error detection and correcting bits; means for simultaneously transferring in parallel the information bits and the error detection and correction bits of each word to the disk units, each bit being allocated to a separate disk unit, and each disk unit having a disk for storing thereon the bits transferred to the disk unit; means for retrieving from the disk units information bits and corresponding first error detection and correction bits; means for recalculating from the information bits second transversal error detection and correction bits; means for comparing the first error detection and correction bits with the second error detection and correction bits; and means responsive to the comparing means for correcting transversal errors in words retrieved from the disk units. 
     
     
       7. The system of claim 6, wherein each disk unit includes a direct access memory for temporarily storing a sequence of bits corresponding to a sequence of words which forms a block of information. 
     
     
       8. The system of claim 7, wherein each disk unit comprises a disk controller, and means for enabling the disk unit to be addressed either by the disk controller or by the first-mentioned controller. 
     
     
       9. The system of claim 6 further comprising means for detecting a defective disk unit and means for reconfiguring the system upon detection of a defective disk unit by allocating a reserve disk unit to replace the defective disk unit. 
     
     
       10. The system of claim 9, wherein the reconfiguring means comprises a plurality of multiplexers, one associated with each disk unit, and wherein the controller has means for controlling the multiplexers so as to allocate and transfer to each disk unit selected bits. 
     
     
       11. The system of claim 9, wherein the calculating means comprises means for calculating longitudinal error detection and correction bits for a sequence of bits corresponding to the sequence of words which forms a block of information, and wherein the defective disk unit detecting means comprises means for detecting longitudinal and transversal errors, and means for comparing the errors to preselected criteria. 
     
     
       12. A method of storing information in and retrieving information from a memory system which includes a plurality of disk units and a controller for the disk units, the information being in the form of a sequence of words, each word comprising a plurality of information bits, each of the information bits having a weight in accordance with the position of the bit in the word, the method comprising calculating from the information bits associated error detection and correction bits; allocating the information bits and the error detection and correction bits to separate disk units, each information bit being allocated to a disk unit in accordance with the weight of the information bit; and transferring the information bits corresponding to words and the associated error detection and correction bits in parallel to the disk units so as to store each bit in its allocated disk unit. 
     
     
       13. The method of claim 12 further comprising detecting a defective disk unit, and automatically reconfiguring the system to replace the defective disk unit with a reserve disk unit. 
     
     
       14. The method of claim 13, wherein the reconfiguring comprises retrieving the bits stored on the defective disk unit, correcting errors in the retrieved bits using the error detection and correction bits and transcribing the bits on the reserve disk unit. 
     
     
       15. The method of claim 13, wherein a sequence of words forms a block of information, and wherein said calculating comprises calculating transversal error detection and correction bits from the information bits of each word, and calculating longitudinal error detection and correction bits from the bits of the same weight in the sequence of words forming the block, and wherein said detecting comprises detecting the defective disk unit by detecting transversal and longitudinal errors and comparing the errors to a predetermined criterion. 
     
     
       16. The method of claim 15, further comprising temporarily storing in a direct access memory in each disk unit a sequence of bits corresponding to the block of information, and, upon retrieving the block of information, correcting errors in the retrieved information bits using the transversal and longitudinal error and correcting bits. 
     
     
       17. A memory system for storing and retrieving information in the form of sequence of words, each word comprising a plurality of information bits, each information bit having a weight corresponding to the position of the bit in a word, the system comprising means for calculating for the information bits corresponding error detection and correction bits; a plurality of disk units for storing the information bits and the error detection and correction bits, a separate disk unit being allocated to each information bit of a word and to the corresponding error detection and correction bits; and means for transferring simultaneously and in parallel to the disk units the information bits of a word and the corresponding error detection and correction bits to store such bits in the allocated disk units. 
     
     
       18. The system of claim 17 further comprising means for detecting a defective disk unit, and means responsive to the detecting means for automatically reconfiguring the system to replace the defective disk unit with a reserve disk unit. 
     
     
       19. The system of claim 18, wherein said means for reconfiguring comprises means for retrieving the bits stored in the defective disk unit, means for correcting errors in the retrieved bits, and means for inscribing the retrieved bits in the reserve disk unit. 
     
     
       20. The system of claim 19, wherein a sequence of words comprises a block of information, and wherein said calculating means comprises first means for calculating transversal error detection and correction bits from the information bits which form a word, and second means for calculating longitudinal error detection and correction bits from the bits of the same weight in the sequence of words which forms the block of information. 
     
     
       21. The system of claim 20, wherein the detecting means comprises means for detecting both longitudinal and transversal errors, and means for comparing the detected errors to predetermined criteria to detect said defective disk unit. 
     
     
       22. The system of claim 21, wherein said detecting means comprises means operable upon detection of longitudinal and transversal errors indicative of a defective disk unit for retrying the disk unit prior to determining that the disk unit is defective. 
     
     
       23. The system of claim 20 further comprising a memory in each disk unit for temporarily storing bits corresponding to a block of information which are transmitted to and from the disk unit. 
     
     
       24. The system of claim 18, wherein the reconfiguring means comprises multiplexing means associated with each disk unit, and wherein the transferring means comprises means for controlling the multiplexing means so as to allocate the bits to particular disk units. 
     
     
       25. The system of claim 17 further comprising means operable upon retrieving of information from the disk units for recalculating the error detection and correction bits from the retrieved information bits, means for comparing the recalculated error detection and correction bits with the first-mentioned error detection and error detection bits retrieved from the disk units to detect errors, and means responsive to the comparing means for correcting the errors in the retrieved information bits.